e1000: fix sw fw sync on igb i210/i211

I finally had a look at the datasheet and spotted an additional
register address difference between regular E1000 and i210/i211 chips.
This patch fixes this and now successfully works on programmed
i210/i211 as well as unprogrammed i211.

Signed-off-by: Marcel Ziswiler <marcel@ziswiler.com>
diff --git a/drivers/net/e1000.h b/drivers/net/e1000.h
index b025ecc..6d110eb 100644
--- a/drivers/net/e1000.h
+++ b/drivers/net/e1000.h
@@ -2497,6 +2497,7 @@
 #define ICH_GFPREG_BASE_MASK       0x1FFF
 #define ICH_FLASH_LINEAR_ADDR_MASK 0x00FFFFFF
 
+#define E1000_I210_SW_FW_SYNC 0x5B50 /* Software-Firmware Synchronization - RW */
 #define E1000_SW_FW_SYNC 0x05B5C /* Software-Firmware Synchronization - RW */
 
 /* SPI EEPROM Status Register */